Polyurethane spinning solutions containing ethylene diamine and bis-(4-aminophenyl)-alkane polyurethanes



ted States Patent Wee 3,485,800

Patented Dec. 23, 1969 erties. One factor which is particularlydetrimental to the 3,485,800 production of filaments on an industrialscale is the rela POLYURETHANE SPINNING SOLUTIONS tively short timewithin which these solutions undergo gel TAINING EI HYLENE DIA WINE ANDBllS-( formation, With the result that spinning becomes imposafla fiidit;fitfiifi lififigfhilfififii, siiia- This is isaiis is aa aassisaiasiysisaaiaasaaasas iii a a and Hans Lem, Dormagen celimany assignors 6solutlons having viscositles of 600 to 1000 poises at FarbenfabrikenBayer Aktiengesellschaft, Leverkusen, -H Q Whfle such O1ut1ons aresultable for use f Germany a corporation of Gel-many mediately 1n theproduction of filaments by the dry spin- No Drawing. Filed June21,1967,Ser.No.647,591 nmg p stablhtv on Storage of Over a week areClaims priority, application Germany, June 25, 1966, usually requiredfor spinning solutions used under normal F 49,555 10 industrialconditions. Int. Cl. COSg 22/04, 53/14 I It is therefore an object ofthis invention to provide CL 25075 7 Chums improved spinning solutions.It is another object to provide spinning solutions having improvedstorage characteristics. It is another object to provide spinningsolutions ABSTRACT 0F THE DISCLOSURE having high resistance to gelformation and degradation. Spinning solutions for the preparation ofspandex fibers It is still another object of this invention to provideimare prepared by reacting an NCO terminated polyester: proved spandexfibers. 4,4-diphenylmethane diisocyanate prepolymer in a polar Theforegoing objects and others which will become solvent with a mixture ofethylene diamine and a diamine apparent from the following descriptionare accomhaving the formula plished in accordance with this invention,generally speak- R 1nN- (;3Nlla or HQN/C\ NH:

R1 LR?) where R and R are lower alkyl and R is an alkylene ing, byproviding spinning solutions for the preparation radical of 2 to 6carbon atoms. The solutions are spun of spandex fibers by reacting in apolar solvent for polyby the wet or dry spinning method to preparefilaments. acrylonitrile an NCO containing prepolymer with a mixture ofethylene diamine and a compound having the formula This inventionrelates to the preparation of polyure- R thane spinning solutions and torubbery elastic filaments J and fibers from segmentedpolyurethane-polyurea elastomers which are resistant to gel formationwhen dissolved 0 in polyacrylonitrile solvents. where R and R are loweralkyl or are joined to the Numerous processes are already known forproducing methylene carbon atom in a cycloaliphatic radical. The elasticfilaments and fibers based on polyurethanes, which prepolymer isprepared by reacting a substantially linear filaments and fibers have alarge number of uses in the 40 polyester having terminal hydroxyl groupsand a molecutextile industry in which they are either spun singly or larweight of from about 1600 to about 2600 with 4,4-diare ensheathed byother filaments wound or spun around phenylmethane diisocyanate in aratio of NCO to OH them. They are mainly used in the production ofcorsets, of from about 1.5/1 to about 1.95/1. The highly viscoussportswear, elastic stockings and in the manufacture of spinningsolutions are subsequently formed into elastic elastic bands for use inunderwear and stockings. The filaments by the wet or dry spinningprocess.

elastic filaments and fibers are usually produced from 40 The diaminocompounds used in admixture with ethylhigh molecular weight segmentedpolymers containing in ene diamine and represented by the formula abovemay the molecule, urethane and urea groups, which polymers also berepresented by the formulae may be prepared by the isocyanatepolyaddition process R from polyesters or polyethers containing hydroxylgroups, l l

diisocyanate and diamines. The prepolymers are extruded by a processknown as chemical spinning, through spin- R2 ning nozzles into acoagulating bath which contains crossh re R 1 War 1k 1 Such a meth l eth1 l linking agents. For obtaining filaments having a high mo- W e 2 1 Oa y S y y p1 py l, h l h l" lecular weight segmentedpolyurethane-polyurea structure, lsopropyl butyl lsobutyl amy exy and t6 Ike or ethylene diamine and possibly also small quantities of HQNHGYCpolyamines have been used in the coagulating bath. Owing to the highreactivity of the prepolymers containing isocyanate groups, and owing tothe consequent instability during storage of the prepolymers, it hasbeen found de- Where R4 is an alkylene radical of 2 to 6 carbon atomssirable to prepare solutions of high molecular weight seg- Such asethylene, P py y n myl n 0f xylmented polyurethane-polyurea adducts insuitable solv- 6116, bonded to the Carbon atom term diat t W0 ents andto work up these solutions into filaments and a omatic rings to form acycloaliphatic radical. fibers by the wet or dry spinning process. Anysuitable compound within the general formula may Furthermore, it isalready known that polyesters conbe used, Such f pl2,2-bis-(4-amin0phenyl) taining hydroxyl groups and diisocyanates may bereacted propane, l,1-bis-(4-aminophenyl)-cyclohexan together at elevatedtemperatures to produce NCO-conaminophenyl)-diethylmethane, bis-(4aminophenyl)- taining prepolymers and then to react these inpolyacryloethyl, isopropyl methane, bis-(4-am1nophenyl)-tert1ary nitrilesolvents at temperatures below 20 C. with ethylbutyl, hexylmethane,bis-(4-aminophenyl)-dipropylmeene diamine to form high molecular weightpolyurethane- F thane, bis-(4-aminophenyl)-rnethyl, ethylmethane, 1,1-polyurea adducts. The filaments obtainable from thesebis-(4-aminophenyl)-cyclopropane, 1,1 bis-(4 aminosolutions by spinninghave good physical and elastic propphenyl)-cyclobutane,1,l-b1s-(4-am1nophenyl)-cyclopen 3 tane, 1, l-bis- (4-aminophenyl)-cyclohexane, aminophenyl)-cycloheptane and the like.

To prepare the spinning solutions according to the invention asubstantially linear polyester containing hydroxyl groups and having anaverage molecular Weight of from about 16 to about 2600, preferably fromabout 1700 to about 2100, is reacted in the melt or in inert solventssuch as methylene dichloride, tetrahydrofuran, dioxan, benzene orchlorobenzene, and if desired mixed with low molecular weight diolscontaining one or more tertiary nitrogen atoms, with diphenyl methane-4,4'-diisocyanate at temperatures below 130 C. The ratio of NCO to OHgroups in the components used in the reaction should be from about 1.5:1 to about 1.95:1 in order that prepolymers containing free NCO groupswill be produced.

The linear polyesters containing terminal hydroxyl groups are preparedby condensation of dicarboxylic acids and diols at elevatedtemperatures. The acid numbers are generally below 8, preferably 0 to 3.The melting point of the polyester is preferably below about 60 C.because otherwise the elastic properties of the end products will beimpaired, especially at low temperatures, and the tendency of thepolymers to gel in solution will also be adversely affected. Anysuitable dicar-boxylic acids may be used in the preparation of thepolyesters such as, for example, succinic acid, adipic acid, pimelicacid, azelaic acid, sebacic acid, thiodibutyric acid, sulphonyldibutyric acid and the like.

Any suitable diol may be used, such as for, example, ethylene glycol,diethylene glycol, propane-1,2-diol, butane-1,3-diol, butane-1,4-diol,hexane-1,6-diol, hexahydrop-xylylene glycol,2,2-dirnethylpropane-1,3-diol, 2,2-diethy1-propane-1,3-diol, thehydroxyalkylation products of the above glycols and the like. Polyestersof lactones, e.g. s-caprolactone, may also be used as startingmaterials. Since the polyesters prepared in this way are highly reactiveone may deactivate them using small quantities of dioxane/SO adduct,benzoyl chloride or traces of hydrogen chloride before the subsequentreaction with diphenyl methane-4,4-diisocyanate.

Any suitable low molecular weight diols containing one or more tertiarynitrogen atoms may, if desired, be mixed in with the polyester, such as,for example, the bishydroxyalkylation products of primary anddisecondary amines with ethylene oxide, propylene oxide and butyleneoxide, and have a molecular weight of less than 500 such as, forexample, N-methyLdiethanolamine, N-butyI-diethanolamine,N-cyclohexyl-diethanolamine, N,N-di-(/8- hydroxyethyl)N,N-diethyl-hexahydro-p-phenylene diamine,N,N-di-(fi-hydroxyethyl)-N,N-di-methyl-ethylene diamine,bis-jS-hydroxyethylpiperazine and the like. However, particularlypreferred are compounds such as l lmethyldiisopropanolamine and N,N di(ii-hydroxypropyl)-N,N-dimethyl-ethylene diamine, although low molecularWeight basic polyethers containing tertiary nitrogen atoms, whichpolyethers are obtainable by condensation of the above mentionedcompounds in the presence of phosphorus acid, may also be mixed with thepolyester. The quantity of diols containing one or more tertiarynitrogen atoms should always be so calculated that the tertiary nitrogenatoms-content based on the finished elastomer substance, does not exceed200 millequivalents/ kg. but in most cases only 80 to 150millequivalents of tertiary nitrogen are present per kilogram ofelastomer substance.

In order to prepare the polyurethane-polyurea solutions, theNCO-containing prepolymers obtained in the melt are introduced slowly,with stirring, at temperatures 'below about 35 C., and preferably belowabout 25 C. into a solution of ethylene diamine and the additionaldiamine in a polyacrylonitrile solvent. The quantity of solvent used isusually so calculated that the polyurethane-polyurea solution has thedesired final concentration after termination of the chain lengtheningreaction.

1,1-bis-(4- The chain lengthening reaction is accompanied by a rapidrise in viscosity, viscosity values between 150 and 600 poises at 20 C.being reached. In many cases the solution is then adjusted to thedesired higher final viscosity by the addition of a small quantity ofhexamethylene- 1,6-diisocyanate, tetramethylene-l,4-diisocyanate orbiuret triisocyanate which is obtained by reacting 3 mols orhexamethylene-l,6-diisocyanate, with 1 mol of water. in most cases,however, the isocyanates are added diluted with a little solvent.

The solids content of the final elastomer solution may amount to 18 to30% by Weight. The polyacrylonitrile solvents used, such asN,-N-dimethylformamide, N,N-dimethyl-acetamide and N-methylpyrrolidone,must be free from constituents Which are capable of reacting withdiisocyanates although these solvents may contain the small quantitiesof water usually present in the commercial products.

The molar ratio of the chain lengthening mixture of ethylene diamine andadditional diamine employed may be varied between 50:50 and :15 but ispreferably between 75 :25 and 80:20. However, the molar ratio of chainlengthening mixture is partly predetermined by the ratio of NCO to OHgroups used in the preparation of the NCO-containing prepolymer. Ingeneral, if the NCO content of the prepolymer is relatively low, theproportion of additional diamine used in the chain lengthening mixturewill also be low, whereas conversely a higher NCO content in theprepolymer will necessitate a higher proportion of additional diaminewhen preparing non-yellowing polyurethane-polyurea solutions. Thequantity of diamine mixture used in the chain lengthening reactionamounts to to mols percent, depending on the NCOzOI-I ratio and thedesired final viscosity of the prepolymer, the given percentage beingbased on the free NCO group-content of the prepolymer.

It is not absolutely necessary to add the melt of the NCO-containingprepolymer into the solution of the chain lengthening mixture whenpreparing the polyurethane polyurea solutions. According to a furtherembodiment. the prepolymer melt can be dissolved in part of thepolyacrylonitrile solvent and the solution rapidly cooled to about 25 C.to about 30 C. This solution is then added to the solution of chainlengthening mixture described before. If, however, the prepolymer wasprepared in one of the above mentioned inert solvents, it is generallyadvisable to remove the solvent by distillation before the chainlengthening reaction takes place although the process is in no wayimpaired by the presence of these inert solvents provided they do notamount to more than 20% by weight of the total quantity of solvent. Onemay, of course, add titanium dioxide, talc or other pigments to theseelastomer solutions before further working up, or one may even add thesepigmenting agents as early as before the chain lengthening reactiontakes place.

The polyurethane-polyurea polymers which may be obtainable in solutionunder the given conditions are of special importance for working up onan industrial scale owing to their good solubility, and the resistanceof their solutions to gel formation and to degradation at roomtemperature or slightly elevated temperature.

The elastic filaments or fibers are produced by known spinningtechniques either dry, i.e., by spinning the elastomer solution into airor inert gases at elevated temperature or Wet, i.e. injecting theelastomer solution into coagulating baths and winding the resultingfilaments, and surface treating the filaments so formed with talc oroily dressing to prevent their sticking together on the spool. The spunfilaments have excellent physical properties such as high elongation ontearing and strength, low permanent elongation and high E-modulus.

The invention will be further illustrated by the following examples inwhich parts are by Weight unless otherwise specified.

EXAMPLE 1 About 250 parts of a polyester of adipic acid, hexane-1,6-diol and 2,2-dimethylpropane-l,3-diol (proportion by weight of diols65/35; OH number 55.5; acid number 0.8) are dehydrated for about onehour at about 120 C. and under a pressure of about 12 mm. Hg and arethen reacted with about 50 parts of diphenylmethane-4,4'-diisocyanate atfrom about 90 to about 95 C. for about one hour. The melt of thepolyesterdiisocyanate adduct is dissolved in about 400 parts ofN,N-dimethylforrnamide and cooled to 20 to 25 C. within about minutes.

This solution is introduced in the course of about 5 minutes at to C.,with stirring, into a solution of about 3.8 parts of ethylene diamine,about 3.6 parts of 2,2-bis-(4'-aminophenyl)-propane and about 432 partsof N,N-dimethylformamide, the viscosity of the solution increasingrapidly during this operation.

The spinning solution which contains about 27% of solids has a viscosityof about 390 poises at 20 C. It is spun by the wet spinning processunder the spinning conditions described hereinafter to yield filamentshaving the following properties:

Titre den 700 Strength g./den 0.40

Elongation at break percent 610 Permanent elongation do 19 E-modulusmg./den 70 EXAMPLE 2 About 250 parts of the dehydrated polyesterdescribed in Example 1 are reacted at 90 to 100 C. in about 130 parts ofanhydrous chlorobenzene with about 50 parts ofdiphenylmethane-4,4-diisocyanate in the course of about one hour. Thesolution of the polyester-diisocyanate adduct is then cooled to about C.and introduced at 15 to 20 C. into a solution of about 3.6 parts ofethylene diamine, about 3.4 parts of 2,2-bis-(4-aminophenyD-propane andabout 702 parts of N,N-dimetbylformamide. The spinning solution producedis a accompanied by a rapid rise in viscosity to about 300 poises at 20C., and the solution having a solids content of about 27%, is spun bythe wet spinning process described hereinafter to form filaments havingthe following properties:

Titre den 700 Strength g./den 0.31

Elongation at break percent 650 Permanent elongation do 18 E-modulusmg./de n 62 EXAMPLE 3 About 3 parts of a 36% SO /dioxan solution areadded to about 250 parts of the polyester described in Example 1 andthis reaction mixture is stirred for about 4 hours at about 100 C. andthen allowed to stand for about one hour at about 100 C. and then freedfrom dioxane and traces of water by keeping it at about 100 C. under apressure of about 12 mm. Hg for about one hour. About 5 parts ofN-methyl-diisopropanolarnine are stirred into the polyester melt, and anNCO-containing prepolymer is obtained by further reaction with about63.6 parts of diphenylrnethane-4,4'-diisocyanate at about 80 to about 85C. for one hour. This prepolymer is dissolved within about 10 minutes inabout 400 parts of N,N-dimethylformamide (H O content 0.01%) and is atthe same time cooled to about 25 C.

The prepolymer solution is introduced at about 16 to about 22 C. withstirring, in the course of about 25 minutes into a mixture of about 4.95parts of ethylene diamine, about 7.28 parts of 1,1-bis-(4-aminophenyl)-cyclohexane, about 8.3 parts of titanium dioxide and about 517 parts ofN,N-dimethylformamide. Viscosity of the solution is 237 poises/20 C.

The solids content of the solution is 27% by weight. The elastomercontains 100 millequivalents of tertiary nitrogen per kilgram.

The spinning solution is worked up into filaments under the conditionsof the wet spinning process described hereinafter, the followingfilament properties being obtained.

Titre den 500 Strength g./den 0.4-4

Elongation at break percent 540 Permanent elongation do 21 E-modulusmg./den 90 EXAMPLE 4 About 250 parts of the polyester described inExample 1 are deactivated in a manner analogous to that described inExample 3 and dehydrated. About 5 parts of N-methyldiisopropanolamineare then stirred in and an NCO- containing prepolymer is obtained byreaction with about 71.5 parts of diphenylmethane-4,4-diisocyanate atabout to about C. for about one hour. The prepolymer is dissolved withinabout 15 minutes in about 400 parts of N,N-dimethylformamide (H Ocontent of 0.01%) and is at the same time cooled to about 25 C. andchain lengthened by introduction of the NCO-containing solution into astirred mixture of about 6.28 parts of ethylene diamine, about 9.3 partsof 1,1 bis-(4-aminophenyl)- cyclohexane, about 8.6 parts of titaniumdioxide and about 548 parts of N,N-dimethylformamide at about 20 toabout 27 C. About one part of hexamethylene-1,6 diisocyanate dissolvedin about 5 parts of N,N-dimethylformarnide is then stirred in, Afterabout four hours, the viscosity is about 340 poises/20 C.

The proportion of elastorner compound in the spinning solution is 27% byweight and the amount of tertiary nitrogen is 97 millequivalents/ kg. ofsolid. The solution is worked up by the wet spinning process describedhereinafter, filaments having the following properties being obtained:

Titre den 600 Strength g./den 0.53

Elongation at break percent 510 Permanent elongation do 20 E-modulusmg./den 102 EXAMPLE 5 About 2 parts of a 39 percent SO /dioxane solutionare added to about 250 parts of the polyester described in Example 1 andthe reaction mixture is stirred for about 2 hours at about C. and thenfreed from dioxane and traces of Water by heating for about one hours atabout 100 C. under a pressure of 12 mm. Hg. An NCO-containing prepolymerobtained by reaction of this solution with about 56.25 parts ofdiphenylmethane- 4,4'-diisocyanate for about one hour at about 85 toabout 90 C., and this prepolymer is then dissolved in about 400 parts ofN,N-dimethylformamide (H O content 0.02 percent) and cooled to about .25C. within about 15 minutes.

(a) One portion of the prepolymer solution is introduced at roomtemperature, with stirring, into a solution of about 4.4 parts ofethylene diamine and about 8.25 parts of 2,2-bis-(4aminophenyl)-propanein about 473 parts of N,N-dimethylformamide. The final viscosity of thesolution is about 180 poises at 20 C. Filaments having the followingproperties are obtained from this spinning solution by carrying out theinstructions given hereinafter for the wet spinning process:

Titre den 290 Strength g./den 0.23 Elongation at break percenL 3 90Permanent elongation do 9 E-modulus mg./den

(b) One portion of prepolymer solution is introduced in the course ofabout 15 minutes at from about 18 to about 24 C., with stirring, into asolution of about 5.2 parts of ethylene diamine and about 6.5 parts of2,2- bis-(4'-aminophenyl)-propane in about 459 parts of N,N-dimethylformamide. The final viscosity of the solution is about 230poises at C. This spinning solution is worked up into filaments havingthe following properties by carrying out the instructions givenhereinafter for the wet spinning process:

Titre den 360 Strength g./den 0.36

Elongation at break percent 440 Permanent elongation do 19 E-modulusmg./den-- 145 EXAMPLE 6 About 3750 parts of the dehydrated polyesterdescribed in Example 1 are reacted for about one hour at about 82 toabout 87 C., with stirring, with about 844 parts ofdiphenylmethane-4,4'-diisocyanate, the product then being dissolved inabout 6000 part of N,N-dimethylformamide and cooled to about C. in about25 minutes. This NCO-containing prepolymer solution is introduced at 20to 25 C. into a solution of about 69 parts of ethylene diamine and about129 parts of 2,2-bis-(4-aminophenyl)-propane in about 7280 parts ofN,N-dimethylformamide which in addition contains about 120 parts oftitanium dioxide (rutile) dispersed therein. The resulting spinningsolution has a viscosity of 620 poises/ 20 C. at a solids content of 27percent. The spinning solution is then worked up by the dry spinningprocess described hereinafter to form filaments which have the followingproperties:

Titre den 210 Strength g./den 0.77

Elongation at break percent 510 Permanent elongation do 19 E-modulusmg./den 126 EXAMPLE 7 About 3750 parts of the dehydrated polyesterdescribed in Example 1 are reacted for about one hour at 80 to 85 C.with stirring, with about 750 parts of diphenylmethane-4,4'-diisocyanateand product obtained is dissolved in about 6000 parts ofN,N-dimethylformamide and cooled to about 25 C. in about 20 minutes.This NCO-containing prepolymer solution is introduced at 18 to 24 C.into a stirred mixture of about 53.1 parts of ethylene diamine, about67.5 parts of 2,2'-bis(4'-aminophenyl)-propane, about 7000 parts ofN,N-dimethylformamide and about 185 parts of titanium dioxide (rutile).About 3 parts of hexamethylene-l,6-diisocyanate, about 27 parts ofN,N-dimethylformamide are then introduced dropwise. A spinning solutionhaving a solids content of 27 percent and a viscosity of 690 poises/20C. is obtained. Filaments having the following properties can beproduced from this solution under the spinning conditions givenhereinafter for the dry spinning process:

Titre den 150 Strength g./den 0.66 Elongation at break percent 490Permanent elongation do 14 E-modulus mg./den 128 Spinning of thespinning solutions described in Examples 17 to form endless filamentsBefore spinning, the solutions are thoroughly filtered through a filterpress and then degasified in vacuo until free from bubbles.

The solutions mentioned hereinabove may be spun either wet or dry.

(I) Wet spinning process-The filtered and degasified solution is spun bymeans of a spinning pump through a multiaperture nozzle of nozzlediameter 50 to 200/ into a water bath 2 to 10 meters in length whichcontains 2 to 10 percent of N,N-dimethylforrnamide and is heated to 2 0to 80 C., in particular 40 to 70 C.

The emerging filaments are drawn off at a rate of 5 to meters perminute, at a draught of 0.5 to 5. After a drying at about C., thefilaments are wound. The physical properties given in the examples aredetermined by known methods.

(II) Dry spinnnig process.-The filtered and degasifiecl solution isdelivered through a spinning pump to the spinneret which is at atemperature of 15 to 90 C., depending on the viscosity. The solution isinjected into the heated shaft through a multiaperture nozzle having anozzle diameter of 80 to 250 The temperature of the air blast is sochosen that the air temperature at the spinning nozzle is 130 to 230 C.The air entering the shaft from above, charged with solvent, iswithdrawn in front or the end of the shaft. The filaments emerging atthe end of the shaft are drawn off at a speed of 200 to 600 meters perminute, preferably 200 to 400 meters per minute. TheN,N-dimethylformamide content of the filaments is below 1 percent.Before the filaments are wound, a dressing agent which prevents stickingis applied to them. The filament properties are then determined by knownmethods.

Explanatory notes on filament testing (1) All dynamic tests were carriedout at a rate of deformation of the filament of 400 percent per minute.

(2) The permanent elongation is determined after stretching the filament3 times by 300 percent of its initial length, and after a recovery timeof 30 s conds.

(3) The modulus is determined at an elongation of the filament to 300percent of its initial length.

EXAMPLE 8 About 21,000 parts of a mixed polyester of hexane 1,6-diol,2,2-dimethylpropane-1,3-diol and adipic acid (molar ratio of diols /35,OH number 63.9, acid number 1.45) are dehydrated in vacuo at about 120C. for about one hour, mixed at about C. with about 445 parts ofN-methyldiisopropanolamine and about 6300 parts ofdiphenylmethane-4,4'-diisOcyanate and heated to about C. for about 50minutes with stirring. About 23,800 parts of the NCO-containingprepolymer melt 50 obtained are introduced with intensive stirring intoa cold solution of about 480 parts of ethylene diamine and about 600parts of 2,2-bis-(4-aminophenyl)-propane in about 70,000 parts ofN,N-dimethylformamide which contains in addition about 1035 parts oftitanium dioxide (rutile) dispersed therein. A spinning solution havinga solids content of 27 percent and a viscosity of 610 poises/20 C. isobtained.

(a) A portion of the solution is briefly heated to 90 C and immediatelythereafter spun dry from a 48 aperture spinneret at a shaft temperatureof about 200 C. When the filaments have left the spinning shaft, adressing agent for reducing adhesion is applied to them. The filamentsare wound at a rate of 300 meters per minute.

Titre den 450 Strength g./den 0.68 Elongation at break percent 480Permanent elongation do 20.5 E-modulus mg./den 134 -(b) A furtherportion of the solution is briefly heated to about 65 C. and immediatelythereafter spun dry from a 12 aperture spinneret at a shaft temperatureof about 17 C. The draw-01f speed is about 450 meters per minute.

Titre den 84 Strength g./den 1.05 Elongation at break percent 365Permanent elongation do ll.-1 'E-modulus mg./den 580 It is to beunderstood that any of the polyesters, solvents, glycols or diamines setforth above may be substituted throughout the examples for thosespecifically used.

Although the invention has been described in considerable detail in theforegoing for the purpose of illustration, it is to be understood thatsuch detail is solely for this purpose and that variations can be madeby those skilled in the art without departing from the spirit and scopeof the invention except as is set forth in the claims.

What is claimed is:

1. A spinning solution for the preparation of polyurethane fibersprepared by the process which comprises reacting in a polar solvent forpolyacrylonitrile an NCO-terminated prepolymer with a mixture ofethylene diamine and a diamine having the formula wherein R and R arelower alkyl, and R is an alkylene radical containing 2 to 6 carbon atomsjoined to the methylene carbon atom to form a cycloaliphatic radical,said prepolymer being prepared by the process which comprises reactingone mol of a substantially linear polyester having terminal hydroxylgroups and a molecular weight of from about 1600 to about 2600 withabout 1.5 to about 1.95 of 4,4-diphenylmethane diisocyanate.

2. The spinning solution of claim 1 wherein the ratio of ethylenediamine to the diamine represented by the formula is from about 50/50 toabout 85/15.

3. The spinning solution of claim 1 wherein the ratio 10 of ethylenediamine to the diamine represented by the formula is from about /25 toabout /20.

4. The spinning solution of claim 1 wherein the prepolymer is preparedfrom an hydroxyl polyester, 4,4-diphenylmethane diisocyanate and aglycol containing tertiary nitrogen atoms and having a molecular weightless than 500.

5. The spinning solution of claim 1 wherein the compound represented bythe formula is 2,2-bis-(4-aminophenyl -propane.

6. The spinning solution of claim 1 wherein the compound represented bythe formula is 1,1-bis-(4-aminophenyl) -cyclohexane.

7. Polyurethane fibers prepared by the process which comprises spinningthe solutions of claim 1.

References Cited UNITED STATES PATENTS 2,962,470 11/1960 Jung 260-45.43,044,990 7/1962 Steuber 260-77.5 3,165,566 1/1965 Murphy et a1. 2641843,397,253 8/1968 Merten et al 260830 DONALD E. CZAJA, Primary ExaminerH. S. COCKERAM, Assistant Examiner US Cl. X.R. 260-326, 37, 40 i

